These doors are conventionally made as folding doors for boarding of pilots. Differently than in ground vehicles, in aircraft the doors present there within the openings provided in the fuselage structure must be absolutely securely closed—filled in—whereby for the necessary sealing, there are so-called gas compression springs generally between the door and door opening.
Closing of these doors therefore requires three successive manual manipulations, specifically pulling the door shut, holding the door in this state, and then locking it. To do this, the door structure is connected to several door locks whose tumblers that interact with catches attached to the fuselage structure can be jointly actuated by way of a suitable linkage that has a handle. Therefore, when these doors are closed, a considerable expenditure of force is necessary for the last two manipulations since the respective door when locking must be held relatively tightly shut. If the door is not shut strongly enough, it can happen that as a result of the force of the gas springs, one tumbler or another engages “space,” and therefore the pertinent door is not properly locked. Moreover, generally both hands of the pertinent person are needed to close the door.
Previously known door locks of locking devices for these doors are obviously user-unfriendly. For opening the door, as long as the pertinent individual is standing in front of the helicopter, there is enough room and freedom of motion for opening and closing the door, and pulling, pressing and turning the handle can be done without major difficulties. This changes immediately, however, after boarding and sitting down in the helicopter; due to the limited ergonomy and the fact that the pilots' seats are made adjustable forward and up depending on body size, operation of these doors becomes many times more difficult.
The doors of a helicopter constitute the first contact with the aircraft and thus determine the first impression on the respective user: there is therefore the requirement that the doors be made self-explanatory in terms of their operability and function and that they not already form the first manual and/or technical obstacle when boarding the helicopter. The functions of door locking should likewise be understandable and logical to anyone, without additional signs and instructions.
A generic door locking device for helicopter doors is available and in use for the helicopter Eurocopter EC 135 as special equipment.
DE 37 07 323 A1 discloses a door locking system, especially for a helicopter door, with two cradle locks that operate in opposite directions, by which the door folds in the closed position are automatically centered with respect to the door frame and braced by compression or tension with the door frame in the direction of the two-dimensional extension of the door fold. The disadvantage here is that the door folds must be held in the closed position when being locked so that two hands are necessary for a closing process.
DE 103 59 737 A1 discloses a device for locking the hood of a motor vehicle. The device has at least one main closure and at least one auxiliary closure that each comprise a latch with a ratchet and a latching member that can be locked by the latch in the closed position of the hood. To initially limit the opening travel of the hood, the latching member of the auxiliary closure is made such that with the main closure unlocked, only after intentional opening travel of the hood does the locking action between the latching member and the latch of the auxiliary closure begin. In this connection, it is disadvantageous that in the half-engaged position, i.e., after activating the latch, a gap remains between the hood and body.